Since mobile phones, digital AV devices, IC cards etc. are having more and more advanced functions, semiconductor silicon chips (hereinafter chips) mounted thereon are getting smaller and thinner. Consequently, there is an increasing demand for large-scale integration of silicon in a package. For example, integrated circuits in which a plurality of chips are one-packaged, such as CSP (Chip Size Package) and MCP (Multi-chip Package), are required to be thin. In order to realize large-scale integration of chips in a package, the thickness of a chip is required to be in a range of 25 to 150 μm.
However, a semiconductor wafer (hereinafter wafer) serving as a base of a chip gets thinner by polishing and decreases its strength, and consequently is more likely to be cracked or bended. Further, wafers with decreased strength due to thinning are difficult to be automatically transferred, and so require being manually transferred. Consequently, such wafers are difficult to handle.
In order to deal with this problem, there is developed a wafer handling system in which a plate called a support plate, made of glass or rigid plastic etc., is attached to a wafer to be polished, thereby reinforcing strength of the wafer and preventing cracks in the wafer and bend of the wafer. Since the wafer handling system reinforces strength of a wafer, a thinned wafer can be transferred automatically.
In the wafer handling system, a wafer and a support plate are attached to each other via various kinds of thermoplastic resin, adhesive etc. The wafer to which the support plate is attached is made thin and thereafter the support plate is separated from the wafer before the wafer is diced. For example, in order to make the wafer as thin as 150 μm or less, it is very preferable to tightly attach the wafer and the support plate to each other.